So i got a 90 Gallon tank and put live rock, about 175lbs which i got from someones tank and 80 lbs of reef live sand from my LFS. Its been running for about 3 weeks and i have not seen any changes in ammonia or nitrites. I was told that i would need fish to start the cycle but also that the live rock and live sand would do the job as well. Is there something that i am missing here. Any help is appreciated.

So i got a 90 Gallon tank and put live rock, about 175lbs which i got from someones tank and 80 lbs of reef live sand from my LFS. Its been running for about 3 weeks and i have not seen any changes in ammonia or nitrites. I was told that i would need fish to start the cycle but also that the live rock and live sand would do the job as well. Is there something that i am missing here. Any help is appreciated.

You need something to kick start the ammonia. Just having LR & sand won't do anything for the cycling process. Some people add a hardy fish or two to start the cycle... The waste from the fish will start the ammonia. Personally I prefer the raw dead shrimp because its more humane, as opposed to putting a fish through toxic levels of ammonia, trites & trates. Drop in one shrimp maybe 2 with a tank your size and the amount of LR you have. Let it rot... Take them out or leave them in for the duration of the cycle. ( I left mine in). And this should get you cycle off and running.

Yes I believe that means it is dying.... If it used to be purple. Sometimes new coralline will be white...... If the rock was left out of the water for a little while that could've killed it. Or lack of light..... Really anything.